Which component is primarily involved in the elongation phase of transcription?

During the elongation phase of transcription, RNA polymerase plays the central role in synthesizing RNA from the DNA template. Once the initiation phase has successfully completed and RNA polymerase binds to the promoter region of the gene, it unwinds the DNA double helix locally and begins to add complementary ribonucleotides to the growing RNA strand. This process occurs in the 5’ to 3’ direction, as RNA polymerase moves along the DNA template strand.

The other options, while important in their respective biological roles, do not participate directly in the elongation of RNA during transcription. Ribosomal RNA is a component of the ribosome and is involved in protein synthesis, not transcription. Transfer RNA functions in translation by bringing amino acids to the ribosome, and DNA ligase is involved in DNA repair and the joining of DNA strands, which does not relate to the process of transcription or its elongation phase. Thus, RNA polymerase is the key enzyme that drives the elongation stage of transcription, making it the correct choice.